SWLing Post Message Board

Nope, I wrote it, the 73 is ok for lower frequencies, as for aiming the loop, I'll repear, the SULA is a directional antenna, so yes, you'll want to aim it at the desired signal

Got it Andrew. I've decided to keep both 9:1 baluns and do a little experimenting with them from low to high HF. I know I'll need to get a rotor to take full advantage of the Sula. I thank you for your help, as well as 13dka's. This'll wrap up my posts on the Sula.

73,
rayb

You're welcome

If you can and want, please come back with some feedback after you'll have tested the SULA for a bit, it will be welcome and useful !

also, since you have two 9:1 ready, and since you seem to have some room, if you want, pick a lenght of insulated wire and lay this antenna down

http://www.kk5jy.net/LoG/

and I mean LITERALLY down on the ground

I was wondering if it would be worthwhile to minimize losses within the antenna elements and if that's even possible? For example, I was using PE or PVC insulated stranded wire with a velocity factor of maybe 0.7 or something. Somewhere I picked up the idea that this slowdown in the dielectric comes with losses. Another thing I picked up (without really understanding it of course) is that "the loops series reactance" would be "impeding the current", so parallel loop wires could help?

13dka wrote: ↑Wed Oct 23, 2024 2:06 pm I was wondering if it would be worthwhile to minimize losses within the antenna elements and if that's even possible? For example, I was using PE or PVC insulated stranded wire with a velocity factor of maybe 0.7 or something. Somewhere I picked up the idea that this slowdown in the dielectric comes with losses. Another thing I picked up (without really understanding it of course) is that "the loops series reactance" would be "impeding the current", so parallel loop wires could help?

Increasing the wire section (diameter) and/or the conductivity may/will improve the antenna, but there are limits to that too; and then in such cases one will probably need to recalculate the SULA termination resistor (same will be needed if changing the antenna size); when I modeled the SULA, I tested several combination, and at end, what I used was the one which offered ease of build and good performance over a wide frequency range, and I know for sure that, changing the SULA parameters will, in most case, have some side effects which won't be exactly positive

For sure, we may consider using (say) some thin copper pipe for the SULA, but as I wrote, that would require recalculating the resistor and/or the perimeter to achieve the expected behavior over, at least, the HF range

Just as an example, the image below shows the SULA built using 2.5mm diameter insulated wire (top) and the same antenna built using 1/2" copper pipe (bottom) w/o changing the resistor or the size, both at the same frequency, as you can see, the backside "null" isn't as deep as it should, so the antenna should be recalculated/optimized, and not just at one frequency but over the desired range